This paper describes hermetic seal wafer bonding using A1 covered with thin Sn as an antioxidation layer. The bonding temperauire is below 400 C, which is the maximum temperature of CMOS-LSI backend process. Gas tightness over 3000 h at room temperature and sealmg stability through heat treatment under a typical reflow condition of 260 C for 10 nun were confirmed for samples bonded at 370 C and 380 C. A key for successful hermetic seal bondmg is relatively high bonding pressure and stress concentration on sealing frames as narrow as several ten microns. The results of SEM and EDX analysis suggested that the bondmg was due to direct Al-Al bonding, while Sn was diffused sparsely among A1 gram boundaries. The developed bondmg technology is usable for wafer-level integration of LSI and MEMS in conjunction with hermetic sealing.
- Al-Al thermo-compression bondmg
- An anti-oxidation layer
- CMOS-LSI backend process
- Hermetic seal